1. Field of the Invention
The present invention relates to magnetron yoke joints.
2. Description of the Related Art
Generally, as shown in FIG. 1, a magnetron is a kind of two pole electronic tube which comprises cathode 1 arranged in series at the center of the magnetron and anode 2 arranged radially around above cathode 1.
An upper yoke 30 and a lower yoke 20 are provided to impress magnetic flux on the action space 3 between the cathode 1 and the anode 2, and magnetic circuits comprising magnets 5 and magnetic poles 6 are provided in the upper side of the upper yoke 30 and the lower side of the lower yoke 20 respectively, and an antenna feeder 7, an antenna seal 8, an antenna ceramic 9 and an antenna cap 10 are provided to discharge micro-wave energy transmitted from anode 2 to the outside(cavity).
Also heat dissipation fins 11 are arranged on the outer side of the anode 2 to dissipate the heat generated by the collisions of thermions (thermal electrons) from anode vanes 2a to the outside, and a choke coil 12 and a high voltage capacitor 13 both protected by a filter box 14 are provided under the lower yoke 20 to prevent the electric source from the backward flow of the unnecessary micro-wave energy generated in the action space 3.
In this way, the thermions emitted from the cathode 1 evolve along cycloidal orbits due to the electric field in the action space 3 impressed by and between the edges of anode vanes 2a positioned inside of anode 2 and cathode 1, and a magnetic field is impressed by the magnetic circuit comprising the magnets 5 and magnetic poles 6, and transmits the energy to anode vanes 2a, and this energy is discharged into an electronic range through an output part comprising an antenna feeder 7 contacting with anode vanes 2a, an antenna ceramic 9 and an antenna seal 8.
The upper and lower yokes 30 and 20, in a magnetron as described above, the upper yoke 30 having an inverted channel section or plane section and the lower yoke 20 having a channel section, are joined to form a square section so as to join not only the elements forming magnetic circuits but also above magnets 5 to a magnetron body mechanically and, at the same time, function as a joining part when a magnetron is mounted on an electronic range,
Referring to FIG. 2, when a magnetron with upper yoke 30, lower yoke 20 and high voltage capacitor 13 is to be mounted on an electronic range, there is such a case, inevitably, that the direction of the joining parts 33 connected to sidewalls 31b and plane part 31a of magnetic circuit part 31 are parallel to the heat dissipation fins 11 and perpendicular to antenna cap 10.
In this case, in a conventional magnetron as shown in FIG. 3, the upper yoke 30 comprises a magnetic circuit part 31 inverted channel sectioned by bending, bent-up parts 32 bent up to overlap with both magnetic circuit part 31 side walls 31b respectively, and joining parts 33 extended from the edge of bent up parts 32 to outside parallel with plane part 31a of magnetic circuit part 31.
Bolt holes 33a are provided in joining parts 33 to join with an electronic range.
Accordingly, in case when the upper yoke 30 mentioned above had been joined onto an electronic range, breakages have been frequently observed in the bent-up parts 32 end the joining parts 33 due to the stress generated by the weight of a magnetron itself on the bent-up parts 32 and the joining parts 33, and damage to the production dies used in the manufacture of the upper yoke 30 have been experienced due to the complicated configuration of the production dies designed to form the upper yoke 30 having magnetic circuit 31, bent up parts 32 and joining parts 33 out of a piece of steel plate.